The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.
Cotton is used in clothing and apparel for comfort properties including the natural moisture regain, vapour transport and air permeability/breathability of cotton fibres. However, cotton has not been widely used in recreational performance apparel due to its high absorbency of perspiration. It is desirable for the fabric in such garments to wick or transport the moisture away from the skin to the outer side of the garment where it is dispersed by evaporation. The high absorbency of cotton can result in the garment becoming too wet and heavy; have a lengthy drying period; and sticks to the skin. This can lead to discomfort and restriction in freedom of movement of a wearer. Slow drying of a wet fabric may also allow more time for bacterial action to create undesirable odours from the absorbed perspiration.
An alternative to using cotton in recreational performance apparel is to use hydrophobic synthetic fibres in the apparel. A variety of treatment chemistries are commercially available that can be used to produce wicking of liquid moisture in normally hydrophobic thermoplastic synthetic garments. However, synthetic fibres such as polyester with wicking finishes do not provide the same level of comfort to the wearer during periods of non-exertion as cotton garments. Polyester absorbs almost no water within the fibre and tends to feel clammy when relatively low levels of liquid moisture are present, because the moisture is present on the surface of the fibres. In addition, many synthetic garments suffer from odour retention problems.
Cotton has also not been preferred in some absorbent products that are worn next to the skin. For example, cotton has not been preferred in the topsheets of adult and baby diapers and sanitary napkins. The topsheet is typically a nonwoven fabric formed from synthetic fibres. Body fluids must pass through the topsheet and into an absorbent core where it is trapped. In order to maximize the comfort of the user of such a product, it is desirable to maximize the wicking of liquid in the Z direction (i.e. the direction normal to the plane of the fabric) and away from the skin. The ideal scenario is for the topsheet to stay dry.
It would therefore be advantageous to provide products prepared from cotton or other cellulosic materials which have reduced absorbent capacity but include wicking properties.
One known form of wicking cellulosic fabric known as WICKING WINDOWS™ fabric is taught in U.S. Pat. No. 7,008,887 B2. This fabric is formed using a fabric treatment regime in which a hydrophobic pattern is printed onto the inner-surface of the treated fabric. The resulting structure comprises a woven or knit fabric having two functional sections, being:
an inner side surface treated to have a discontinuous hydrophobicity, comprising sections of yarn treated with a hydrophobic treatment and sections of yarn not treated with a hydrophobic treatment, or other methods such as a hydrophobic top sheet with punched apertures, or with embedded hydrophilic fibres which from the wicking windows; and
an outer side surface having a higher absorbent capacity than the inner side surface,
the fabric has channels of hydrophilic fibres from the inner side surface to the outer side surface for wicking liquid contacting the inner side surface of the fabric to the outer side surface of the fabric.
This structure produces untreated wicking windows or channels of fabric (aperture, untreated fibres or similar) in the hydrophobic layer inner side surface to the hydrophilic layer which wick any moisture from the inner side surface to the outer side surface for evaporation.
Whilst the fabric provides for effective wicking from the inner side surface to the outer side surface, the discontinuous hydrophobicity on the inner layer created by the wicking window channels can allow for two way moisture transport. Hence, although the garment surface next to the body can be up to 50% drier and less clinging than that of normal cotton fabrics, the garment can still feel wet and cling to the skin because moisture can be transported towards a user's skin from the fabric. Once the fabric becomes overly-saturated or fully-wetted the moisture content of the fabric blocks the penetration of air/moisture vapour from body side, resulting in impermeable feeling and completely losing the moisture management ability.
It would therefore be desirable to provide an alternate wicking fabric which preferably addresses one or more disadvantages of known wicking cellulosic fabrics such as wicking windows.